Influence of salinity and moisture on the threshold shear velocity of saline sand in the Qarhan Desert,Qaidam Basin of China: A wind tunnel experiment

Determination of the threshold shear velocity is essential for predicting sand transport, dust release and desertification. In this study, a wind tunnel experiment was conducted to evaluate the influence of salinity and moisture on the threshold shear velocity of saline sand. Saline sand samples (mean particle size of 164.50-186.08 μm and the total silt, clay and salt content of 0.80%-8.25%) were collected from three saline sand dunes (one barchan dune and two linear dunes) in the Qarhan Desert, Qaidam Basin of China. Original saline sand samples were placed in two experimental trays for wet and dry processing to simulate deliquescence and desiccation, respectively. Surface moisture content ranging from 0.30% to 1.90% was generated by the steam method so that the saline sand can absorb water in a saturated water vapor environment. The motion of sand particles was determined by the observers with a solid laser. The laser sheet (0.80 cm thick), which was emitted by the solid laser, horizontally covered the sand surface and was bound to the sand. Results show that the cohesion of saline sand results from a combination of salt and water. The threshold shear velocity increases exponentially with the increase in crust thickness for the linear sand dunes. There is a positive linear correlation between the original moisture content and relative threshold shear velocity. The threshold shear velocity of dewatered sand is greater than that of wet sand with the same original moisture content. Our results will provide valuable information about the sand transport of highly saline soil in the desert.     

Monitoring desertification processes in Mongolian Plateau using MODIS tasseled cap transformation and TGSI time series

Most remote sensing studies assess the desertification using vegetation monitoring method. But it has the insufficient precision of vegetation monitoring for the limited vegetation cover of the desertification region. Therefore, it offers an alternative approach for the desertification research to assess sand dune and sandy land change using remote sensing in the desertification region. In this study, the indices derived from the well-known tasseled cap transformation(TCT), tasseled cap angle(TCA),disturbance index(DI), process indicator(PI), and topsoil grain size index(TGSI) were integrated to monitor and assess the desertification at the thirteen study sites including sand dunes and sandy lands distributed in the Mongolian Plateau(MP) from 2000 to 2015. A decision tree was used to classify the desertification on a regional scale. The average overall accuracy of 2000, 2005, 2010 and 2015 desertification classification was higher than 90%. Results from this study indicated that integration of the advantages of TCA, DI and TGSI could better assess the desertification. During the last 16 years, Badain Jaran Desert, Tengger Desert, and Ulan Buh Desert showed a relative stabilization. Otindag Sandy Land and the deserts of Khar Nuur, Ereen Nuur, Tsagan Nuur, Khongoryn Els, Hobq, and Mu Us showed a slow increasing of desertification, whereas Bayan Gobi, Horqin and Hulun Buir sandy lands showed a slow decreasing of desertification. Compared with the other 11 sites, the fine sand dunes occupied the majority of the Tengger Desert, and the coarse sandy land occupied the majority of the Horqin Sandy Land. Our findings on a three or four years' periodical fluctuated changes in the desertification may possibly reflect changing precipitation and soil moisture in the MP. Further work to link the TCA, DI,TGSI, and PI values with the desertification characteristics is recommended to set the thresholds and improve the assessment accuracy with field investigation.     

浅谈地下车站侧墙大块定型移动模架施工技术

随着城市地铁的飞速发展,地铁车站在条件满足的情况下大都采用明挖法施工。在施工主体侧墙时采用满堂红支架法施工,但因施工时工期较长且易存在一些质量通病,因此,近年来大块定型移动模架被得到了广泛的应用。     

关于藏书倒架的研究与探讨——以中国矿业大学图书馆文昌科技图书阅览室为例

结合工作实际探讨藏书倒架的前期准备工作及倒架时的路线设计、人员组织安排和倒架后的环节完善。以期减轻图书馆人员在倒架工作中的劳动强度和工作量，提高工作效率。     

Study on the Land Use Right in Urban Housing Dismantling and Moving

With the strengthening of constitutional protection that legal private property is not to be encroached upon and the land usufructs paid regime are further clear, the regime of urban housing dismantling and moving is facing a vigorous test. This paper analyzes three problems: the justice of the withdrawal of land use right, the legality of the alteration of the land use right and the rationality of the compensation of the land use right during the urban housing dismantling and moving. Finally, this paper tries to find some effective measures to solve the chain problems.     

土方机械落物保护结构动态仿真及试验

简述了土方机械落物保护结构的特点及性能要求,建立了落物保护结构受瞬态冲击响应的有限元结构动力学方程并提出了求解算法。以某装载机落物保护结构为例,建立了落物保护结构的非线性有限元模型,讨论了有限元网格划分及载荷施加方法,分析了落物保护结构的主要设计参数对冲击点最大位移及落锤速度和加速度的影响,并给出了更合理的结构。在试验台上对该装载机落物保护结构进行了落物冲击试验,试验结果和仿真结果吻合较好。落物保护结构的动态仿真为结构的设计提供了依据。     

基于无人机技术黄河沿岸沙丘移动速度监测及影响因素分析

为更便捷地监测乌兰布和沙漠黄河沿岸沙丘移动速度并解析其影响因素,该研究以乌兰布和沙漠沿黄段沙丘为研究对象,应用无人机航拍技术开展沿岸沙丘的季节性地貌过程和影响因素研究。结果表明:1)研究区沙丘年移动速率1.08～2.27 m/a,多年平均输沙势为78.82 VU,年合成输沙势为25.92 VU,处于低风能环境,8～12 m/s等级风输沙势是年输沙势的主要部分,约占73.24%。方向变率(合成输沙势(Resultant Drift Potential,RDP)与输沙势(Drift Potential,DP)的比值)RDP/DP保持在0.30～0.46之间,属于中等变率。合成输沙方向RDD为57.83°～107.39°,与沙丘移动方向较为一致,西风组占全年输沙势的52.09%,是沙丘年移动的主要驱动力。2)沙丘移动速率具有明显的季节特征,整体呈现春季移动速率快,冬末-春初次之,秋季与秋末-冬末相近,夏季移动速率最慢。其中,秋末-冬末、春季和秋季输沙势DP 8.48～20.49 VU,合成输沙势方向在90.02°～95.54°之间,RDP/DP值均在0.3～0.8之间,属于中等变率,西风组作用显著,这与年合成输沙方向及沙丘走向较为一致;冬末-春初和春末-夏季分别受东北风(NE)和南风组(SSE、S、SSW)作用,沙丘通过形态变化适应风向,移动速度降缓。季节输沙势主要集中在8～10m/s风速等级,约占整个季节输沙势的40.76%～56.93%。3)综合各季节和年际输沙势与沙丘移动距离呈线性正相关,拟合方程为y=1.02+0.006 62x(R~2=0.339,F=5.616,P=0.045),方程总体显著,输沙势可以表征该地区沙丘移动距离。基于无人机监测的沙丘运动研究综合显示,风况是该地区影响该地区沙丘移动的主要动力,其中西风组8 m/s以上风速是研究区沙丘移动的主要驱动力。风向变率和合成输沙势方向与沙丘移动方向一致时沙丘移动则快,不一致时则缓;无人机可在较大尺度上为沙丘移动提供更为便捷的监测服务,研究结果可为同类地区沙丘移动的无人机监测提供参考依据。     

南黄海族小黄鱼昼夜渔获率差异的统计学分析

利用2004年度东海区重点渔场底曳拖网渔业资源监测资料,从中选用小黄鱼网次渔获率作为指标值,应用LSD方法对南黄海族小黄鱼昼夜渔获率差异进行了统计学分析,以揭示小黄鱼昼夜的活动规律。结果表明,小黄鱼在不同的洄游阶段昼夜网次间渔获率无显著性差异,昼夜无垂直移动现象,常年处于底层,为典型的底层鱼类;在利用底曳拖网船进行渔业资源调查时,无需修正昼夜网次间小黄鱼的渔获率,用获取的调查数据即可估算资源量。     

柴达木盆地沙丘移动的空间分异及对形态参数的响应

研究沙丘移动规律与空间分异特征有助于准确了解风沙活动的危害程度,为区域城镇规划和青藏高原国家生态安全屏障保护与建设提供参考。该研究基于GoogleEarth软件测量横向沙丘的形态参数与移动速度,分析了移动速度与方向的空间分异特征,以及移动速度对形态参数的响应。结果表明,1)柴达木盆地内沙丘移动速度介于0～23.53 m/a之间,平均4.66 m/a,以中速(1～5 m/a)为主(53.73%),中部移动最快(5.22±4.27 m/a),东南部最慢(3.27±3.08 m/a),移动方向与主风向一致;2)沙丘移动速度与宽度的相关性最好(R~2=0.988),以后的研究中需多关注沙丘宽度这一参数;3)从柴达木盆地整体看,降水量越大、风速越低,沙丘移动越慢;从局部看,植被覆盖度越大,沙丘移动越慢;4)密集的河流可阻挡沙丘移动,保护格尔木市区,但不能消除沙丘移动的威胁。     

黄河乌兰布和沙漠段沿岸风沙流结构与沙丘移动规律

为明确黄河乌兰布和沙漠段沿岸的风沙活动及沙丘移动特征,该文以黄河乌兰布和沙漠段沿岸的流动沙丘为研究对象,采用野外观测与实验室分析相结合的方法对沿岸沙丘的起沙风况、沙物质组成、风沙流结构及沙丘移动规律进行初步的定量研究。结果表明:起沙风的主风为西南—西风,集中于3-5月份,且5～6m/s风占起沙风的50.26%;沙物质粒径以细砂(0.1～0.25mm)为主,沿黄段沙丘粒径极细砂以下(≤0.1mm)的沙物质粒径组成比沙漠腹地减少8.92%;距地60cm高度范围内,81.75%的沙物质在0～10cm高的气层中通过。在沙丘的不同部位上,相对输沙量与高程之间有着良好的幂函数关系;沙丘向前移动的距离为8.19m/a,主要发生在3-5月份。该研究结果可为合理计算入黄风积沙量及完善黄河沿岸综合防护体系提供科学依据。